Add comments to test case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@66760 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Analysis/ptr-arith.c b/test/Analysis/ptr-arith.c
index ca23437..11c8708 100644
--- a/test/Analysis/ptr-arith.c
+++ b/test/Analysis/ptr-arith.c
@@ -13,6 +13,9 @@
   ++p;
 }
 
+// This test case checks if we get the right rvalue type of a TypedViewRegion.
+// The ElementRegion's type depends on the array region's rvalue type. If it was
+// a pointer type, we would get a loc::SymbolVal for '*p'.
 char* memchr();
 static int
 domain_port (const char *domain_b, const char *domain_e,